This invention relates generally to pneumatic plug devices and, particularly, to elongated, multi-sized expansible pneumatic plugs used for sealing the interior of a range of pipeline diameters. More particularly, the elongated pneumatic plugs of this invention are provided with elastomeric sleeve structures that result in the ordered and staged inflation and deflation of the pneumatic plugs.
Pneumatic plugs are used in the construction and plumbing industries to seal pipelines and conduits for repair, installation and testing purposes. The type of plug used, whether mechanical or pneumatic in operation, depends upon the pipeline sealing requirements and the structure of the pipeline or pipeline connections. For example, wye or tee connections may require that two interconnected pipes be sealed simultaneously. For these purposes, elongated pneumatic plug devices are commonly used.
In the past, several configurations of elongated pneumatic plug devices have been proposed or utilized for sealing pipeline structures. Typically, these pneumatic plug devices have included expandable sleeve structures having a constant outside diameter and generally uniform wall thicknesses. Others have used sleeve structures that define a pair of opposing and readily larger end sections wherein generally two varying wall thicknesses are used as disclosed, for example, in U.S. Pat. No. 4,660,603. The latter structure was subsequently improved by the pipe plug device of U.S. Pat. No. 4,790,356 wherein a sleeve structure having a constant outside diameter is disclosed having a uniformly tapered side wall thickness. Still other plug devices have been used wherein two separate pneumatic plug devices are interconnected by a semi-rigid conduit.
The problem to be overcome by these prior art structures is the provision of two separate sealing elements which respectively engage to seal two separate pipe sections. Further, it is preferable that the middle component or section, which is unsupported during use, be protected by undergoing the least amount of inflation. Still further, it is desired that the expandable end elements or sections be controllable with respect to the order of inflation and deflation. And, although the prior art devices have attempted to provide an ordered and staged inflation and deflation of their respective end elements, while protecting the unsupported middle section, problems and limitations remain.
It is the object of this invention to provide an elongated pneumatic pipe plug having an elastomeric sleeve that results in the ordered and staged inflation and deflation of the plug body while protecting the unsupported middle portion of the sleeve during use. It is a further object of this invention to provide a pneumatic pipe plug exhibiting such functional parameters and which is economical and able to be manufactured in a reliable manner.